Bloody Toll: Boko Haram Behind Deadliest Killing Spree Since 9/11

In the two months since Boko Haram fighters kidnapped hundreds of schoolgirls in northeastern Nigeria, the terror group has taken at least 1,000 lives in what may be the deadliest killing spree by a single terrorist group since the Sept. 11 attacks, according to an NBC News analysis of reports from the region.

While the fate of the 272 girls kidnapped on April 14 remains unknown, Boko Haram has added to its bloodthirsty reputation since the abduction with a string of attacks -- including three that killed more than 100 men, women and children apiece. The pace of the attacks has increased dramatically since the kidnappings, instilling fear not just in the civilian population, but in the Nigerian government and security services as well, according to U.S. counterterrorism officials.

"The group's ability to conduct high-casualty attacks has evolved to an unprecedented level, even compared to 2012 when they bombed the U.N. building in Abuja," said one senior counterterrorism official, who spoke on condition of anonymity. "This period far surpasses that. The group has learned how to make their tactics more deadly and has expanded their reach beyond the control of security forces."

The worst was an attack last month on two public markets in the towns of Gamboru and Ngala in Borno state that killed more than 300 people. That incident alone was the third-worst terror attack since al Qaeda used hijacked jetliners to attack on the Twin Towers and the Pentagon on Sept. 11, 2001, trailing only a coordinated string of car bombings targeting Yazidi communities in northern Iraq on Aug. 14, 2007, that left 796 dead, and the school massacre in Beslan, Russia, in 2004, which killed more than 380 people, mostly children.

Boko Haram Continues to Abduct Young Girls

At the same time, the group has continued to abduct young girls, according to a senior U.S. counterterrorism official, who spoke with NBC News on condition of anonymity. There have been at least three similar abductions of groups of 10 to 20 girls since the raid on a school in Chibok in which hundreds were snatched. The most recent abduction occurred on Monday, when Boko Haram fighters seized 20 more girls from a village not far from Chibok, loaded them onto trucks and drove away, the official said.

On Thursday, fears that the group could mount massive attacks on World Cup "viewing centers" prompted the government to ban public screenings of games in the northern part of the country. Such centers have been the target of Boko Haram at least twice in the last two months. Boko Haram leader Abubakar Shekau has previously preached against football, as soccer is known in Africa, as part of the Islamist group's agenda to impose strict sharia law in northern Nigeria.

Current and former U.S. officials say the killings are not random. Pointing to the assassination of a leading Muslim emir in northern Nigeria last month, they say Boko Haram is systematically eliminating opposition to its plan to establish an Islamic caliphate across the region.

John Campbell of the Council on Foreign Relations, a former U.S. ambassador to Nigeria, said that the attacks have been focused on "eliminating … villages that have opposed Boko Haram, punishing villages who have helped (the) Nigerian JTF (military task force)."

"We often don't know why, but it's not random," he said.

As a result of the bloody campaign, "Boko Haram has cleared a territory the size of Rhode Island of any traditional religious authority and there is no state authority," he said, referring to an area in Borno state in the far northeast of the country along the border with Cameroon.

Michael Leiter, former director of the National Counter Terrorism Center and now an NBC News consultant, said that the abduction of the schoolgirls focused public attention on the group's cold-blooded ways. But the recent wave of attacks is a dramatic escalation.

"Although the kidnapping of the girls captured the attention of the Twitterverse, nothing has yet slowed Boko Haram's deadly and largely indiscriminate rampage," he said. "The fact is that Boko Haram was murderous long before the kidnapping and it remains so. Equally clear is that defeating the group and eliminating violent extremism in Nigeria is a complex, long-term problem that demands an enduring international coalition working with the Nigerians."

From Car Bombs to Machetes and Chain Saws

Although casualty figures are often impossible to verify because many of the attacks are carried out in remote areas, Boko Haram undoubtedly has inflicted a staggering toll since it began its current rampage, using weapons that range from automatic weapons and car bombs to machetes and chain saws wielded at close range.

On April 14 - the same day the schoolgirls were kidnapped -- Boko Haram fighters carried out a pair of attacks on an open-air bus depot outside Abuja, the nation's capital, one during morning rush, one during evening rush. Those attacks killed 90 people.

The body count continued to climb in the following weeks.

The deadliest attacks occurred on May 7,when 336 people were killed in Gamboru and Ngala; on May 20, in bombings in the city of Jos, hundreds of miles to the southwest, killed 118; and on June 2, when 200-plus were slaughtered in at least three other villages in Borno state.

In several recent attacks the terrorists used disguises to increase the death toll.

In the attack on Gamboru and Ngala, a federal senator from Borno state told NBC News that the assault began with insurgents dressed in Nigerian military uniforms opening fire on a public market in the afternoon, when the bazaar was filled with villagers from the town and neighboring area. The militants then moved through the rest of the city, according to the senator, Ahmed Zanna, burning down houses and shops and destroying buildings with rocket-propelled grenades. Most of the city -- including the police station -- was destroyed.

In the most recent attack, on June 5, on the outskirts of the city of Maiduguri, the BBC reported that militants posing as imams, or Islamic clergy, gathered locals in the center of the village, ostensibly to hear them preach, then turned their automatic weapons on the crowd. Forty-five people were killed in the fusillade, it said.

It's not just the scale, but the frequency and geographic range of the attacks that have alarmed counterterrorism experts. In the five days between June 1 and 5, there were Boko Haram attacks every day, leaving more than 250 dead. Then, last weekend, an unknown number of Cameroonians were killed when a contingent of 300 militants crossed the border and attacked a village, burning churches.

Campbell, the former U.S. ambassador, said he does not expect the violence to diminish in the near term.

"Boko Haram is going from strength to strength, broadening its area of operations in the north," he said. "What would satisfy it? We have no political manifesto. We have to fall back on the rhetoric they've used: they want control over many or most of the Islamic states in the North."

As for the death toll, Campbell believes it's actually higher than reported, perhaps by a significant number.

"In my opinion, the official numbers have way understated the death tolls," he said. "The numbers are provided by the military and Nigerian government policy is to minimize it. NGO's (non-government organizations) operating in the north tell me, 'take official figures and multiply by five.'"

Map shows Nigeria's Borno state, stronghold of Boko Haram.Google

As an example, Campbell cites the death toll in an attack on a boarding school in Buni Yadi, in Yobe state, in February. Boko Haram militants separated the boys from girls and then slaughtered all the boys and burned the school's 24 buildings to the ground. The boys were either shot or burned to death.

"The death toll was reported as 49," said Campbell, "but quite credible sources --American sources-- say the number was at least a hundred."

Similarly, the Nigerian federal government initially tried to play down the death toll in Gamburu, saying 100 had been killed, not the 300 plus counted by local authorities.

Another disturbing trend, Campbell said, is the elimination by Boko Haram of religious authorities opposed to its violent campaign. Last week's killing of the emir of Gwoza was part of an attack of three emirs who were traveling to a funeral. The two other emirs were wounded as well but hid in the bush and survived. In February, another emir opposed to Boko Haram, escaped death when militants burned his palace to the ground, killing 60 of his staff and others.

Experts, including Campbell, say the plan is to "decertify" the emirs as powerful religious forces either by killing them or silencing them.

The U.S. response to the violence has, thus far, been limited to providing intelligence and communications support to the Nigerian government. But even with daily flights of Predator and Global Hawk drones providing intelligence, the Nigerian military has not engaged Boko Haram and has not claimed any success in the fight since the kidnappings.

"One of their greatest advantages is the paralysis their attacks has created among the security institutions charged with countering the group and protecting civilians," said the senior U.S. counterterrorism official.

Rep. Chris Smith (R-New Jersey), chairman of the House Foreign Affairs Subcommittee on Africa, visited northern Nigeria last weekend, meeting with government officials and parents whose children are missing or have been killed. Smith pushed for Boko Haram to be named a Foreign Terrorist Organization two years ago but failed to convince the State Department, which chose instead to designate only the group's leaders. Boko Haram was ultimately designated an FTO last November.

In an interview with Cynthia McFadden of NBC News, former Secretary of State Hillary Clinton said that experts had believed formally designating Boko Haram as a terror group would empower it, and that it was more effective to sanction individual members of the group. She said the later decision to make the formal designation was correct "based on what has happened since."

Smith said in a speech on the House floor Thursday that the fear and paralysis in the north is having other, less public, consequences that ultimately could have a devastating long-term effect on what is already one of the world's poorest areas.

"Largely due to the terrorist violence in the North, an estimated 3.3 million Nigerians are displaced - making Nigeria the world's third largest displaced population, behind only Syria and Colombia," said Smith. "Many of those displaced people are farmers, which will certainly disrupt the next harvesting season and further impoverish Nigeria's suffering people."

Smith told NBC News that the U.S. must engage further with the Nigerian security services despite their lackluster record, but he also called on the administration to beef up the U.S.'s own investigative capacity under the Foreign Terrorist Organization designation "to identify those providing material and other assistance to Boko Haram."

Without both and a commitment by Nigeria, said Smith, he sees a continuing cycle of greater violence and more kidnappings.